Surfboard fin system

Abstract

The present invention relates to a surfboard fin system which includes a generally horizontal hydrofoil intersecting or connecting with one or more vertical fins. The generally horizontal hydrofoil of the invention is designed using principles of hydrodynamics, that is, the forces generated by the flow of water over a hydrofoil or wing, to create a force that pulls downward on the fin system and, in turn, downward on the tail end of the water planing hull or surfboard.

1 . A fin system for a water planing hull comprising: 
 at least one generally vertical element, said vertical element having a leading edge, a trailing edge, a hull attachment end and a tip; and    at least one hydrofoil, said hydrofoil having a lower surface, a chord line, a mean camber line located on the side of the chord line of the hydrofoil away from the attachment end and toward the tip of the vertical element, said hydrofoil having a first distance from the lower surface to the mean camber line less than a second distance from the lower surface to the chord line whereby the hydrofoil is shaped to create negative lift as the surfboard moves through water in the forward direction.    
   
   
       2 . The fin system of  claim 1 , wherein said hydrofoil has a dihedral angle.  
   
   
       3 . The fin system of  claim 1 , wherein said hydrofoil has an anhedral angle.  
   
   
       4 . The fin system of  claim 1 , wherein said hydrofoil has an angle of attack to create negative lift in addition to the negative lift created by the hydrofoil itself.  
   
   
       5 . The fin system of  claim 1 , wherein the hydrofoil has a root end adjacent to the vertical element and a tip, the forward-most point of the tip of the hydrofoil located forward of the forward-most point of the root end.  
   
   
       6 . The fin system of  claim 1 , wherein the hydrofoil has a root end adjacent to the vertical element and a tip, the forward-most point of the root end located forward of the forward-most point of the tip of the hydrofoil.  
   
   
       7 . The fin system of  claim 1 , wherein the hydrofoil has a root end adjacent to the vertical element and a tip, wherein the length of the chord line of the hydrofoil decreases from the root end to the tip of the hydrofoil.  
   
   
       8 . The fin system of  claim 1 , wherein the hydrofoil has a root end adjacent to the vertical element and a tip, wherein the length of the chord line of the hydrofoil remains substantially constant from the root end to the tip of the hydrofoil.  
   
   
       9 . The fin system of  claim 1 , including first and second generally vertical elements joined by a hydrofoil.  
   
   
       10 . The fin system of  claim 9  further including a hydrofoil extending outwardly from at least one vertical element.  
   
   
       11 . A surfboard fin system comprising: 
 a plurality of hydrofoils attachable to a vertical fin, the fin defining a proximal end attachable to a surfboard and a distal end defining a vertical fin tip, each of said hydrofoils having an arcuate leading edge, a root end attachable to the vertical fin, a distal end defining a hydrofoil tip, a first surface facing the surfboard and a second surface facing the vertical fin tip;    said hydrofoils having a cross-sectional profile to create lift, said cross-sectional profile including a chord line and a mean camber line; and    said mean camber line located primarily within the area of the cross-sectional profile between the chord line and the second surface of the hydrofoil.    
   
   
       12 . The surfboard fin system of  claim 11 , wherein said hydrofoil has a dihedral angle.  
   
   
       13 . The surfboard fin system of  claim 11 , wherein said hydrofoil has a anhedral angle.  
   
   
       14 . The surfboard fin system of  claim 11 , wherein said hydrofoil has an angle of attack to create negative lift in addition to the negative lift created by the hydrofoil itself.  
   
   
       15 . The surfboard fin system of  claim 11 , wherein the leading edge of each hydrofoil at the tip is forward of said leading edge of the hydrofoil at the root end.  
   
   
       16 . The surfboard fin system of  claim 11 , wherein the leading edge of each hydrofoil at the root end is forward of said leading edge of the hydrofoil at the tip.  
   
   
       17 . The surfboard fin system of  claim 11 , wherein the length of the chord line of the hydrofoil decreases from the root end to the tip of the hydrofoil.  
   
   
       18 . The surfboard fin system of  claim 11 , wherein the length of the chord line of the hydrofoil remains substantially constant from the root end to the tip of the hydrofoil.  
   
   
       19 . A surfboard fin comprising: 
 a vertical section with an attachment side for attachment to a surfboard; and    a pair of horizontal sections attached to the vertical section located at any point along the vertical section, each of said horizontal sections comprising an inverse hydrofoil, said inverse hydrofoil shaped to create negative lift as the surfboard is moved through the water in the forward direction, said negative lift transmitted through the vertical section to pull the tail of the surfboard downwardly, said horizontal sections having a cross-sectional profile with a lower surface on the side of the hydrofoil away from the attachment side, a chord line, and a mean camber line intermediate the chord line and lower surface.    
   
   
       20 . A surfboard comprising: 
 a water planing hull;    a fin system, said fin system comprising at least one vertical fin, said vertical fin having a leading edge, a trailing edge, an attachment end and a tip; and    at least one hydrofoil, said hydrofoil having a lower surface, a chord line mean camber line located on the side of the chord line of the hydrofoil away from the attachment end, toward the tip of the vertical fin and intermediate the lower surface and the chord line whereby, said hydrofoil is shaped to create negative lift as the surfboard moves through water in the forward direction.    
   
   
       21 . The fin system of  claim 20 , wherein said hydrofoil has a dihedral angle.  
   
   
       22 . The fin system of  claim 20 , wherein said hydrofoil has an anhedral angle.  
   
   
       23 . The fin system of  claim 20 , wherein said hydrofoil has an angle of attack to create negative lift in addition to the negative lift created by the hydrofoil itself.  
   
   
       24 . The fin system of  claim 20 , wherein the hydrofoil has a root end adjacent to the vertical fin and a tip, the forward-most point of the tip of the hydrofoil located forward of the forward-most point of the root end.  
   
   
       25 . The fin system of  claim 20 , wherein the hydrofoil has a root end adjacent to the vertical fin and a tip, the forward-most point of the root end located forward of the forward-most point of the tip of the hydrofoil.  
   
   
       26 . The fin system of  claim 20 , wherein the hydrofoil has a root end adjacent to the vertical fin and a tip, wherein the length of the chord line of the hydrofoil decreases from the root end to the tip of the hydrofoil.  
   
   
       27 . The fin system of  claim 20 , wherein the hydrofoil has a root end adjacent to the vertical fin and a tip, wherein the length of the chord line of the hydrofoil remains substantially constant from the root end to the tip of the hydrofoil.  
   
   
       28 . The fin system of  claim 20 , wherein two vertical fins are joined by a hydrofoil, and hydrofoils extend outwardly from each vertical fin.